Grease manufacture



Patented Feb. 24, 1953 2,629,691 I C E GREASE MANUFACTURE Walter-H.Peterson, Point Richmond, Calif., as-

signor to Shell Development Company, San Francisco, Calif., acorporation of Delaware No Drawing. Application December 19, 1949,Serial No. 133,961

(or. 252 z8) 13 Claims. 1

This invention relates to the preparation of greases and similarcompositions. More specifically, the invention is concerned withimprovements in the process for the preparation of greases comprising orcontaining inorganic colloids and lubricating oils.

Greases comprising lubricating oils gelled with inorganic colloidsincorporated therein have been described previously by Munch (GermanPatent 451,055) and Kistler (U. S. Patent 2,260,625). The inorganiccolloidal materials in most cases have been various forms of silica.Kistler, for example, shows the use of silica aerogels, while Munch wasthe first to describe silica greases prepared by the displacement ofwater from silica hydrogel using volatile organic liquids which in turnwere displaced with a mineral oil. In comparison with ordinary greases,the lubricating oil-inorganic gel greases possess the outstandingcharacteristic of structural stability at 1 elevated temperatures. Thisproperty makes such greases of particular interest in the lubricating ofball bearings and other machinerry parts, as well as in turbojet enginesand in steel rolling mills.

One of the shortcomings of such systems is that they are sensitive tothe presence of water, apparently due to the hydrophilic nature of thegel surfaces. Hence, the unmodified greases prepared according to thetwo publications given above have been found to be unstable if employedin the presence of water. The end result is the disintegration of thegrease structure, resulting in the precipitation of silica and theseparation of an oil phase.

Various means have been taken to correct this characteristic. Theaddition of various protective compounds is described in severalcopending patent applications. Patent application Serial No. 782,694.,filed October 28, 1947, in the name of Fred H. Stross (now Patent No.2,554,222 dated May 22, 1951), describes the use of amines for thispurpose. A similar result was obtained by the addition of hydrophobicsoaps as disclosed in patent application Serial No. 782,695, filedOctober 28, 1947, by the same inventor (now abandoned). Greases ofamphoteric metal such as alumina may be water-proofed by the addition ofhigh molecular weight acids, as shown by copending patent applicationSerial No. 91,229, filed May 3, 19%9, filed in the names of Fred H.Stress and Stanley T. Abrams. One of the most promising types ofadditives to be utilized for the subject purpose includes hydrophobichydroxy compounds exemplified by the glycerides of l2-hydroxy stearlcacid. These are disclosed in patent application Serial No. 82,905, filedMarch 22, 1949, in the name of W. E. Peterson (now Patout No. 2,573,650dated October 30, 1951). The present application is acontinuation-in-part of the latter application, Serial No. 82,905.

"In utilizing these various water-proofing agents, it has been thenormal practice to in- 2 corporate the agent either in the inorganic gelor more usually in the lubricating oil. Following this, the three majoringredients, namely, additive, gel and oil, were stirred and subjectedto shearing in order to produce a satisfactory grease structure. Attimes, moderate amounts of. warming have been employed. The majorpurpose for heat, as used in the past, has been to thin the oil so as tomore easily incorporate the addition ingredients therein.

It is an object of the present invention to improve the water-resistanceof greases gelled by the presence of inorganic colloidal material. It isa further object of the present invention to improve the process for thepreparation of such greases. It is an additional object to provideimproved water-resistant lubricating greases showing an unexpectedresponse to water-proofing agents. These objects will be more fullyunderstood and other objects will become apparent from the followingdescription of the invention.

Now, in accordance with this invention, it has been found that thewater-resistance and other characteristics of greases gelled withinorganic colloidal materials are substantially improved when theingredients are heated for a period between about 20 and about 180minutes at a tem perature between about C. and about 220 0., preferablybetween C. and 200 0. Still in accordance with this invention, it hasbeen found that this heat treatment is especially effective if a surfaceactive hydrophobic material useful as a water-proofing agent is presentduring a substantial part of the heating period. Another feature of thepresent invention comprises the improvement in gelling power ofinorganic colloids caused by the subject heat treatment. Again, inaccordance with this invention, it has been found that the heattreatment is of maximum benefit when the inorganic colloidal materialhas been treated with l-30% by weight of an acid such as phosphoric acidor boric acid previous to incorporation in the mixture of grease-forminginsredients.

The inorganic colloidal materials especially useful for grease formationinclude metallic oxides or hydroxides as well as treated clays asdefined hereinafter. IvIore specifically, the inorganic colloids capableof gel formation in lubricants are alkaline earth metal oxides andhydroxides, alkaline earth metal carbonates, alkali metal carbonates,polyvalent metal oxides such as silica, magnesia, alumina, ferric oxide,vanadium pentoxides and other heavy metal oxides, polyvalent metalsulfides such as ferrous sulfide and cuprous sulfide, and some metallicsulfates and phosphates. Mixtures of these materials may be employed, ofwhich the most promising have been found to be synthetic zeolites suchas magnesium silicates or aluminum silicates prepared by known methods.

Various naturally occurring colloidal inorganic compounds are alsouseful if employed as more particularly described hereinafter. These areordinarily complex combinations of two or more metallic oxides roughlydescribed as magnesium silicates, aluminum silicates, magnesium-aluminumsilicates and the like, which may be considered to be chemicalcombinations of magnesium oxide with silicon dioxide or aluminum oxidewith silicon dioxide, etc. Some representative naturally occurringmaterials which are particularly suitable are the bentonites, fullersearth, Hectorite and Wyoming montmorillonite. The magnesiummontmorillonites such as Hectorite have been found to be especiallyeffective grease gelling agents, particularly when treated as describedhereinafter.

In order to perform its function .as a gelling agent, the inorganiccolloid should be in a highly expanded form. One method for thepreparation of colloidal materials comprises conversion of inorganicmetalloidal halides or other combustible materials into aerosols, suchas by burning silicon tetrachloride to form an aerosol of colloidalsilica. Other typical methods for the preparation of expanded colloidsinclude the aerogel formation described in the Kistler patent referredto above and also gels incorporated in oil without an intermediatedrying step between hydrogel formation and greas formation. A typicalmethod for the preparation of aerogels comprises forming silica hydrogelby the addition of sulfuric acids to sodium silicate solution. Theaerogel is then prepared by displacing water from the hydrogel with avolatile organic liquid such as ethyl alcohol and heating the resultingorganogel to a temperature above the critical temperature of the liquidcontained therein while maintaining the pressure on the systemsufficiently high to insure that the liquid phase will remain liquiduntil the critical temperature is reached. At this point, the liquidwill be converted into the gaseous state without the formation ofmenisci at the gas-liquid interface.

In the preparation of greases without a drying step, one of theacceptable processes comprises formation of a hydrogel, displacement ofwater with a water-miscible organic solvent such as alcohol, andreplacement of the alcohol with either a lubricating oil or anothervolatile oil-miscible solvent such as benzene. In the latter case, thebenzene is then replaced by a lubricating oil. An improvement on both ofthese alternatives comprises the direct transfer of a hydrogel into oilWithout intermediate drying or intermediate organogel formation. It hasrecently been found that this direct transfer is possible byincorporating one of the hydrophobic surface active agents recitedhereinafter together with the two major ingredients, namely, theinorganic gelling agent and lubricating oil and subsequently removingWater.

Various grease-forming base liquids may be utilized in the preparationof inorganic gel greases. In general, it is preferred to use the usualrange of mineral lubricating oils which are employed in the preparationof ordinary soap greases. Synthetic liquid hydrocarbons may be used alsoincluding various alkylated aromatic hydrocarbons such as tertiary butylnaphthalenes, polymerized olefins such as suitable liquid polyethylenes,polybutylenes, polycetenes and the like. Various other oleaginousliquids including natural occurring materials such as vegetable andanimal oils and synthetic lubricants may be used. Examples of the latterclass include the diesters of dicarboxylic acids suchas-bis(2-ethylhexyl) sebacate, bis(methylethyl) succinate; the inorganicesters such as the phosphate esters including tributyl phosphate,trioctyl phosphate, tricresyl phosphate and dioctyl cresyl phosphate.Mixtures of such lubricants may be employed as well. For specialpurposes involving high temperature use or for analogous utility, thepoly-- meric silicones may be used with advantage.

In accordance with the basic concept of the present invention, these twoprincipal ingredients are heated together at a temperature between aboutC. and 220 C. for a. period between about 20 and about 180 minutes. Thepreferred ranges within which optimum effect has been obtained include atemperature range of about and 200 C. and the preferred heating periodis between 30 minutes and 120 minutes. The heating may be conducted atatmospheric pressure or under vacuum or superatmospheric pressure. Ifthe grease is to be formed from an inorganic alcogel the heating periodis conveniently conducted under vacuum so that alcohol is withdrawnsimultaneously during the heat treatment. The mixtur of ingredients maybe stirred during the heating period or may be subjected to shearingsuch as milling for the purpose of creating a proper dispersion of thegel throughout the lubricating oil so as to create a grease structure.

The present process is especially applicable to the preparation ofgreases containing hydrophobic surface active agents of the classesreferred to hereinbefor and fully described in the copending patentapplications enunciated here in. Preferred classes of these surfaceactive agents include especially hydrophobic cationic surface activeagents such as higher aliphatic amines, quaternary ammonium compoundsand polyamines as well as their salts and amides. Typical speciesinclude heptadecyl amine, diinethyl benzyl octadecyl ammonium chloride.amines obtained by the ammonoloysis of chlorinated paraflin wax, higherfatty acid salts of polymeric adducts such as those derived fromacrolein and ammonia and from diallyl amine and hydrogen sulfide; andhigher fatty acid partial amides of polyalkylene polyamines such asoleic acid amide of tetraethylenepentamine. An especially preferred typeof polymeric amine for use in the present invention may be obtained byreaction of ammonia with epichlorhydrin resulting in the formation of alinear alkylene polyamine bearing hydroxyl substituents. The principalproduct of such a reaction normally has the general formula OH HQ[N C DC ]V|NHZ wherein n is an integer between 2 and 10. In order to beefiective as a water-proofing agent for the subject greases, thisparticular type of polyamine should be in partial amide formation with ahydrophobic organic acid such as the hi her fatty acids derived fromanimal and vegetable oils. Another highly effective type of hydrophobicagent comprises the condensation products of a polyamine with alkyl oralkenyl substituted succinic or succinamic acids or'their anhydrides oracid esters. Typical species include the reaction products of ammoniaand epichlorhydrin condensed with octadecenyl succinic acid. Anotherpreferred species of this category include the condensation products ofalkaline diamines with the same classes of acids. Typical ;of these arethe condensation products of dodec ylsucciuicanhy i eand y e e d amineand octadecenyl succinamic acid and ethylene diamine. When amphotericmetal gels are used as the gelling agent, it has been found that waterinsoluble organic acids provide outstanding water resistance. These aretypified by tetradecane-lphosphinic acid, petroleum hydrocarbon sulfonicacids, stearic acid and the like.

In the production of water-resistant greases from metallic gels such assilica, water-insoluble soaps such as aluminium stearate, aluminum l2-hydroxy stearate, lead stearate and the like, may be used.

As stated hereinbefore, the combined effect of incorporating one ofthese hydrophobic waterproofing agents together with the heat treatmentforming the basis of the present invention, provides greases exhibitingoutstanding resistance to the deleterious action of water. Greasesprepared according to the present process are preferably thosecontaining 210% by weight of the inorganic gelling agent based on thetotal grease composition and 10-50% by weight of the inorganic gellingagent of one or more of the waterresistance improving materials.

Example I A silica alcogel was prepared by forming a hydrogel of silicahaving approximately a 5% silica content and replacing water bydistillation in the presence of isopropyl alcohol. Five parts by weightof the silica alcogel (based on silica content) were added to 94 partsby weight of a mineral lubricating oil containing 1 part by weight ofglyceryl l2-hydroxy stearate. The mixture was milled to disperse thealcogel in the lubricating oil after which the resulting composition washeated for one hour at one of the temperatures indicated in the tablebelow. Five samples were treated in a similar manner, the sole variationbeing in the temperature of heating. After heating, the compositionswere milled to a minimum grease penetration. A grease was also preparedhaving the same composition but was not given any heat treatment. All ofthe samples so prepared were subjected to a roll stability test in thepresence of water. This test is intended to evaluate the mechanicalstability of greases in contact with water such as may occur when wheelbearings are exposed to rain, cooling water, etc. In this method, 15grams of water and '75 grams of the grease tested are kept in a rotatingcylinder containing a weighted iron roller. The consistency of thegrease is determined quantitatively before and at hourly intervalsduring rolling. The hours necessary to reduce the consistency of thegrease to an arbitrary penetration has been taken as a measure of themechanical stability of the grease sample in the presence of water. Thefollowing comparison was obtained by this method when the greasesdescribed above were tested.

Water Roll Stability Temperature of Heating, G.

Test, Hours Water Roll Stal empelature of Heating, O. bimy Test Hours171. 20. 192..- Greater than 21. 210 Do. No heating 2.

Example III A grease was prepared having the same composition as thatdescribed in Example II. Part of the grease was not subjected to heattreatment while two portions thereof were heated at 170 C. for 26 and 83minutes, respectively. The samples so prepared and treated weresubjected to the water roll stability test described in Example I. Thefollowing data were obtained:

Water Roll Time at 170 0., Minutes Stability Test, Hours Example IVEpichlorhydrin and about five molecular proportions of ammonia werereacted at about 40-60 C. for about one hour, the product was heated toabout C., and thereafter tallow fatty acids were added thereto and themixture heated at C. to 225 C. for about one hour to form the amide-theproportions being such as to form approximately the one-third amide. Agrease was prepared containing about 2.5% of the partially saponifiedcondensation product, 5% of silica and the remainder of minerallubricating oil. The resulting grease was heated at a temperature of C.for one hour. This grease was found to have a high resistance todisintegration by hot water, while a similar grease prepared from thesame proportions of ingredients and heated at 130 C. for one hour had asubstantially lower hot water resistance.

Example V Alumina hydrogel was added to a mineral lubricating oilcontaining stearic acid after which the ingredients were heated withstirring for two hours at 150 C. Upon milling, a highly water resistantgrease was formed containing 5 parts by weight of alumina, 2.5 parts byWeight of stearic acid and 92.5 parts by weight of mineral oil.

Example VI A silica alumina hydrogel containing about 10% alumina wasadded to mineral oil having alumina stearate dissolved therein. Themixture of components was heated for 30 minutes at C. and then milled toa minimum grease penetration. The resulting grease contained 6% byweight of the silica alumina gel and 2% by weight of aluminum stearate.When subjected to the action of hot water for a period of 50 hours nodisintegration occurred.

7." Example VII A grease was prepared by heating 4 parts by weight ofsilica alcogel and 1 part by weight of dimethyldioctadecylaminehydrochloride with 95 parts by weight of a mineral lubricating oil. Theresulting composition was heated for one-half hour at 170 C. andexhibited good resistance to the action of hot water.

I claim as my invention:

1. In the process for the preparation of a grease comprising lubricatingoil, a gelling amount of a colloidal metallic oxide gel in highlyexpanded form and capable of forming a grease with said oil and ahydrophobic surface active agent, the improvement which comprisesheating said ingredients at atemperature between about 165 and about 200C'. for aperiod between about 30 minutes and about 120 minutes.

2'. In the process for the preparation of agrease comprising lubricatingoil, a gelling amount of a colloidal metallic oxide gel in high-' lyexpanded form and capable of forming a grease with said oil and ahydrophobic hydroxy fatty ester, the improvement which comprises heatingsaid ingredients at a temperature between about 165 C. and about 200 C.for a period between about 30 minutes and about 120 minutes.

3.111 the process for the preparation of a grease comprising lubricatingoil, a gelling amount of a colloidal metallic oxide gel in highlyexpanded form and capable of forming a grease with said oil and ahydrophobic amino surface active agent, the improvement which comprisesheating said ingredients at a temperature between about 165 and about200 C. for a period between about 30 minutes and about 120 minutes.

4. In the process for the preparation of a grease comprising a minerallubricating oil, a gelling amount of colloidal silica gel in highlyexpanded form and capable of forming a grease with said oil and aglyceride of 12-hydroxy stearic acid, the improvement which comprisesheating said ingredients at a temperature between about 165 and about200 C. for a period between about 30 minutes and about 120' minutes.

5. In the process for the preparation of a grease comprising a minerallubricating oil, a

gelling amount of colloidal silica gel in highly" expanded form andcapable of forming a grease with said oil and a higher fatty acid amideof a condensation product of epichlorhydrin and ammonia, the improvementwhich comprises heating said ingredients at a temperature between about165 and about200 C. for a period between about 30 minutes and about 120minutes.

6. The process which comprises mixing a lubricating oil, a colloidalmetallic oxid gel in highly expanded form and capable of forming agrease with said oil anda hydrophobic surface active with said oilbearing. l-30% of a mineral acid adsorbed thereon, and a hydrophobicsurface active agent, heating the mixture so prepared at atemperaturebetween about 120' and about 220 C. for a period between about 20minutes and about 180 minutes, and shearing the heat 8 treated mixtureuntil a grease structure is formed-.

8. In the process for the preparation of 'a; grease comprising minerallubricating oil, a gelling amount of a colloidal metallic oxide capableof forming a grease with said oil, and a hydrophobic hydroxy fattyester, the improvement which comprises heating said ingredients at atemperature between about 165 C. and about 200 C. for a period betweenabout 30 minutes and about 120 minutes.

9. In the process for the preparation of a grease comprising minerallubricating oil, a gel ling amount of a colloidal metallic oxide capableof forming a grease with said oil, and a hydrophobic surface activeagent, the improvement which comprises heating said ingredients at atemperature between about 165 and about 200 C; for a period betweenabout 30 minutes and about 120 minutes.

10. In the process for the preparation of a grease comprising minerallubricating oil and a gelling amount of a mixture of colloidal inorganicoxides capable of forming a grease with said oil and a hydrophobicsurface active agent, the improvement which comprises heating saidingredients at :a temperature between about 165 and 200 C. for a periodbetween about 30 minutes and 120'minutes.

11. In a process for the preparation of a water resistant grease, thestep comprising heating a composition comprising a lubricating oil, agelling amount of an inorganic gel capable of forming a grease with saidoil and from about 10% to about by weight of the inorganic gelling agentof a non-metallic hydrophobic aliphatic hydroxy organic compound, saidgrease being heated at a temperature between about and 220 C. for aperiod between about 20 min utes and about 3 hours.

12. In a process for the preparation of a grease, the step comprisingheating a composition comprising a mineral lubricating oil thick ened toa grease-like consistency by from about 2 to about 10 by weight, basedon the total composition of an inorganic oxide gel in a highly expandedform having its normal liquid content replaced by said lubricating oil,and from 10%' -resistant grease, the step comprising heating acomposition comprising a lubricating oil, a gelling amount of aninorganic gel capable of forming a grease with said oil anda'hydrophobic surface-active agent, said composition being heated at atemperature between about 120 and- 220 C. for a period between about 20minutes and3 hours.

WALTER H. PETERSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,248,636 Marsden July 3, 19412,260,625 Kistler Oct. 28, 1941 2,531,440 Jordan Nov. 28, 1950 StressMay 22 1951

1. IN THE PROCESS FOR THE PREPARATION OF A GREASE COMPRISING LUBICATINGOIL, A GELLING AMOUNT OF A COLLOIDAL METALLIC OXIDE GEL IN HIGHLYEXPANDED FORM AND CAPABLE OF FORMING A GREASE WITH SAID OIL AND AHYDROPHOBIC SURFACE ACTIVE AGENT, THE IMPROVEMENT WHICH COMPRISESHEATING SAID INGREDIENTS AT A TEMPERATURE BETWEEN ABOUT 165 AND ABOUT200*C. FOR A PERIOD BETWEEN ABOUT 30 MINUTES AND ABOUT 120 MINUTES.